Blue-green infrastructure and biodiversity: Urbanization and forestation have an important influence on bird diversity in water habitats

Water and forest habitats are an indispensable part of the blue-green infrastructure, a network that provides solutions for urban climatic challenges by building with nature. We were interested in the effect of water areas and the surrounding environment on bird species richness; specifically, we studied the influence of different levels of urbanization and related forestation. We focused on water, arboreal and ground bird assemblages in forested and nonforested water habitats in a 2000 km2 lowland area of Polabí in the Czech Republic at three urbanization levels: (i) urban, (ii) rural and (iii) open landscapes. The results revealed that ground birds were positively influenced by urban areas, while arboreal birds benefitted from surrounding forestation and tree vegetation on water banks. Overall, the results for native bird assemblages were not different, except that native water birds appeared to thrive in no settlement. The positive relationship between ground birds and urbanization and the weak negative relationship or lack of relationship between urbanization and the other groups were somewhat unexpected. The most likely reason is that water habitats are not as homogenized as other urban habitats. Surrounding forests could also help buffer the influences of urbanized areas. We conclude that blue-green infrastructure is also an essential environment for many birds.